/*
 class MyLinkedList {
    static class ListNode {
        private int val;
        private ListNode prev;
        private ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }
}

public class Test {
    public static void main(String[] args) {
        ListNode node =new ListNode(20);
    }
}
*/
